Modeling phase formation on catalyst surfaces: Coke formation and
suppression in hydrocarbon environments
Abstract
We develop a simulation toolset employing density functional theory
(DFT) in conjunction with grand canonical Monte Carlo (GCMC) to study
coke formation on Fe-based catalysts during propane dehydrogenation
(PDH). As expected, pure Fe surfaces develop stable graphitic coke
structures and rapidly deactivate. We find that coke formation is
markedly less favorable on Fe3C and FeS surfaces. Fe-Al
alloys display varying degrees of coke resistance, depending on their
composition, suggesting that they can be optimized for coke resistance
under PDH conditions. Electronic structure analyses show that both
electron-withdrawing effects (on Fe3C and FeS) and
electron-donating effects (on Fe-Al alloys) destabilize adsorbed carbon.
On the alloy surfaces, a geometric effect also isolates Fe sites and
disrupts the formation of graphitic carbon networks. This work
demonstrates the utility of GCMC for studying the formation of
disordered phases on catalyst surfaces and provides insights for
improving the coke resistance of Fe-based PDH catalysts.